London: A driver who stopped to help at the scene of a crash discovered the dying victim was his teenage son.

Guy Marshall, a former ambulance service volunteer, was going home from work when he saw there had been an accident involving a motorbike and a car.

He immediately realised the injured rider was his 18-year-old son, Tom, and started battling to save his life. "He was moving slightly and had a pulse," said Marshall, 53, an optometrist from Orford, near Woodbridge in Suffolk.

"I gave him some oxygen and held him and spoke to him but he was not conscious at all. I knew at that stage he had gone." Tom died in his father's arms before paramedics arrived.

Police are still investigating the crash between Tom's Suzuki GS500 and a Mazda MX5 shortly after 5pm on June 12.

Initial inquiries suggest Tom, who suffered multiple injuries, was on the wrong side of a 60 miles per hour single carriageway when they collided. The road surface was dry and visibility excellent.

Marshall had worked as a volunteer first responder for the East Anglia Ambulance Service for several years until around 18 months ago. The job involved providing first aid to patients - often heart attack victims.